No RTC Needed – ESP32 NTP Clock

#include <WiFi.h>
#include "time.h"
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

// --- Configuration ---
const char* ssid     = "ENTER_NEW_WIFI_NAME_HERE"; 
const char* password = "ENTER_NEW_PASSWORD_HERE";

const char* ntpServer = "pool.ntp.org";
const long  gmtOffset_sec = 19800; // IST: UTC + 5:30
const int   daylightOffset_sec = 0;

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);

// --- Pins ---
const int START_STOP_BUTTON = 18; 
const int MODE_RESET_BUTTON = 5;

// --- State Variables ---
enum Mode { CLOCK, STOPWATCH, QUOTES };
Mode currentMode = CLOCK;

unsigned long startTime = 0;
unsigned long elapsedTime = 0;
bool running = false;

// You can add more quotes here as needed
const char* quotes[] = {
  "Stay hungry. Stay foolish.",
  "Code is poetry.",
  "Keep moving forward.",
  "Innovation is key.",
  "Build, Hack, Repeat."
};
int totalQuotes = 5;
int quoteIndex = 0;

void setup() {
  Serial.begin(115200);
  
  pinMode(START_STOP_BUTTON, INPUT_PULLUP);
  pinMode(MODE_RESET_BUTTON, INPUT_PULLUP);

  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
  }
  
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.setCursor(10, 20);
  display.println("Connecting WiFi...");
  display.display();

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("\nWiFi Connected!");
  configTime(gmtOffset_sec, daylightOffset_sec, ntpServer);
}

void loop() {
  checkButtons();
  
  display.clearDisplay();
  
  switch (currentMode) {
    case CLOCK:
      showClock();
      break;
    case STOPWATCH:
      showStopwatch();
      break;
    case QUOTES:
      showQuotes();
      break;
  }
  
  display.display();
  delay(50); // Smoother refresh for stopwatch
}

void checkButtons() {
  static bool lastModeState = HIGH;
  static bool lastStartState = HIGH;
  
  bool modeState = digitalRead(MODE_RESET_BUTTON);
  bool startState = digitalRead(START_STOP_BUTTON);

  // Mode Switch / Reset Logic (D5)
  if (lastModeState == HIGH && modeState == LOW) {
    if (currentMode == STOPWATCH && !running) {
      elapsedTime = 0; // Reset only when paused
    } else {
      currentMode = (Mode)((currentMode + 1) % 3);
      if(currentMode == QUOTES) quoteIndex = random(0, totalQuotes);
    }
    delay(200); // Debounce
  }

  // Start / Stop Logic (D18)
  if (lastStartState == HIGH && startState == LOW) {
    if (currentMode == STOPWATCH) {
      running = !running;
      if (running) startTime = millis() - elapsedTime;
    }
    delay(200); // Debounce
  }

  lastModeState = modeState;
  lastStartState = startState;
}

void showClock() {
  struct tm timeinfo;
  if(!getLocalTime(&timeinfo)){
    display.setCursor(0, 25);
    display.println("Syncing Time...");
    return;
  }
  
  display.setTextSize(1);
  display.setCursor(35, 0);
  display.print("NTP CLOCK");
  
  display.setTextSize(2);
  display.setCursor(15, 25);
  display.printf("%02d:%02d:%02d", timeinfo.tm_hour, timeinfo.tm_min, timeinfo.tm_sec);
  
  display.setTextSize(1);
  display.setCursor(25, 55);
  display.print("Region: IST");
}

void showStopwatch() {
  if (running) elapsedTime = millis() - startTime;
  
  unsigned long totalSeconds = elapsedTime / 1000;
  unsigned long minutes = (totalSeconds / 60) % 60;
  unsigned long seconds = totalSeconds % 60;
  unsigned long tenths = (elapsedTime / 100) % 10;

  display.setTextSize(1);
  display.setCursor(35, 0);
  display.print("STOPWATCH");
  
  display.setTextSize(2);
  display.setCursor(20, 25);
  display.printf("%02lu:%02lu.%lu", minutes, seconds, tenths);
  
  display.setTextSize(1);
  display.setCursor(0, 55);
  display.print(running ? "Running..." : "Paused (D5 to Reset)");
}

void showQuotes() {
  display.setTextSize(1);
  display.setCursor(35, 0);
  display.print("QUOTES");
  
  display.setTextSize(1);
  display.setCursor(0, 25);
  display.println(quotes[quoteIndex]);
  
  display.setCursor(0, 55);
  display.print("D5 for Next Quote");
}